Feature | October 09, 2006 | Rick Dana Barlow

Mobile C-arms rivaling their fixed siblings via automated capabilities, clinical applications, digital reach

If the half dozen or so manufacturers of mobile C-arms could push the technological development envelope forward they undoubtedly would venture to equip them as close to fixed C-arms as possible.
Right now, however, such a strategy is a bit too cost-prohibitive – for both suppliers and customers – and those additional bells and whistles largely may not be needed in the outpatient market segment. Yet.
But that isn’t stopping manufacturers from trying to move forward. In fact, convenience, flexibility and pinpoint accuracy are three key attributes that mobile C-arms have adopted and implemented within the last few years.

Key Developments Within the Last Two Years

What’s driving much of the technological development in mobile C-arms during the past few years is the demand for digital and three-dimensional imaging capabilities as inpatient and outpatient surgical procedures migrate toward minimally invasive techniques that require precise navigation.
“To have the ability to obtain cross-sectional scans intra-operatively with a mobile C-arm, and to use this information to assist with a diagnosis within the operating room is invaluable,” Anthony Anderson, product manager, Ziehm Imaging Inc., told Outpatient Care Technology. He classified the integration of 3-D imaging on a mobile stand one of the leading developments advancing mobile C-arms.
Higher-tech imaging cameras and digital capabilities make the list, too, according to Anderson. “The improvements of the imaging systems software has led to C-arms requiring less radiation output to obtain optimum image quality,” he noted. “This leads to less radiation dosage received by the user and the patient.”
Furthermore, Anderson contended that future Ziehm releases move “true digital imaging” into the operating room. “The future is digital imaging,” he added. “It is only a matter of time before all C-arms will employ this technology.”
Roby Trierweiler, senior director, surgery and urology, Siemens Medical Solutions, picked the marriage of 3-D imaging during surgical procedures with 3-D surgical navigation as a boost.
“One key development has been intra-operative 3-D imaging with the seemingly flawless integration of 3-D surgical navigation, which provides fast, efficient and precise positioning of implants and/or screws,” Trierweiler said. “Especially in complex spine procedures, intra-operative 3-D imaging with 3-D navigation continues to increasingly become a clinical necessity.”
Brad Fox, general manager, surgery marketing, GE Healthcare, concurred, but also stressed something a bit more down-to-earth as particularly appealing: Motorization.
“With fixed units you can automatically control angulation and table slide,” he said, “but mobile units require a technician to manually push and pull the unit. New motorized configurations eliminate the need for such repositioning and generate productivity gains, particularly in the cardiovascular area. You don’t have to stop a procedure to move the C-arm around.”
The migration of advanced features and image processing techniques from other imaging modalities is perhaps the most exciting development to Mark Manum, marketing manager, surgery business unit, Philips Medical Systems NA.
“Philips has made huge investments in the development of industry-leading technology in CT, MR, X-ray and ultrasound,” Manum said. “Some of the technology that is transferred from other modalities to C-arms is not obvious to the user but makes a tremendous difference. For example, advanced noise reduction algorithms add value by improving image quality and clinical utility. Other technology migrations, such as three dimensional image acquisition and volumetric rendering techniques, are more obvious to users, since they allow C-arms to be used in entirely new ways. As digital flat detectors become more economical and replace imaging intensifiers, the quantum leap in image quality will create even more new applications for mobile fluoroscopy.

Overcoming Limitations

In recent years mobile C-arms have made significant technological strides, breaking through a number of walls that allow clinicians to expand their capabilities in new areas.
“Usability is a big issue facing C-arms, particularly in outpatient centers,” Manum noted. “Mobile C-arms are increasingly being used to perform tasks that once required a cath lab or RF room. Additional features have been added to C-arms to suit these advanced applications, sometimes at the expense of ease-of-use. This issue is compounded further by the fact that C-arms are often operated by users with little or no X-ray training.”
Manum added that even though his company makes a “simple, easy-to-understand user interface common to many of its products, Philips further simplifies use by automating many functions” on selected models, including pre-programmed exam types to set optimal parameters for a particular application and limit the need for manual adjustments, auto contrast/brightness control and a technology that automatically positions shutters when raw radiation is detected at the image intensifier.
What makes C-arms cool now is hot, in terms of fluoroscopic use time.
“In the past, practitioners were limited to 15 to 30 minutes of use time before overheating with fan-cooled C-arms (depending on brand and model),” Anderson said. “With the outpatient and pain management explosion coupled with equipment cost, facilities find themselves relying on single C-arms to perform many, and often, back-to-back procedures. The advancement of cooling technology extends fluoroscopy time which could lead to cost saving for the facilities because they would not need multiple C-arms.” In fact, Ziehm plans to roll out a C-arm with a monoblock generator and rotating anode with advanced active cooling technology.
In addition, according to Anderson, archiving today has advanced to the point where the user can now print images on paper or film, store images to CD/DVD R, USB, floppy disc or send and retrieve images from a PACS network via DICOM.
Networkability remained a steep speed bump for a while, Trierweiler noted, but not for long. “Total DICOM compatibility made it possible to import and display pre-op images from any modality on the monitor cart virtually eliminating the need to physically bring X-ray films into the O.R. and for the surgeon to consult the light box,” he said. “Monitor carts of mobile C-arms have emerged to be a full-blown imaging workstation. The need for a local printer or documentation has been eliminated as the monitor cart yields the ability to fully integrate the O.R. into the hospital’s network.”
Trierweiler also stressed isocentricity as particularly valuable to mobile C-arms for use in intra-operative 3-D imaging. In fact, if you compare 3-D navigation with the limitations of existing 2-D navigation systems you’ll see a marked difference, he added.
Finally, 3-D imaging’s value “has been drastically enhanced with the ability of multimodality image fusion with the 3-D imaging volume provided by a 3-D C-arm,” he continued. “Image fusion provides the ability to show soft tissue contrast images in form of an overlay on the 3-D imaging volume generated by the 3-D C-arm as a landmark or as other important clinical functional imaging information before, during, or after the procedure.”
Fox indicated that clinicians should expect mobile units to be armed with more imaging capabilities and more power to increase throughput because they can be operated for longer time periods and they enable the clinician to see new and smaller surgical tools within the body cavity. Incorporating navigation systems simplifies set-up and workflow, he added.
And while Fox admitted that flat panel technology may become more pronounced in mobile C-arms it won’t necessarily be widespread. “It may be too costly for bread-and-butter surgical procedures,” he said, “but it’s good for vascular procedures and makes the unit more versatile.”
Ironically, improvements in fluoroscopic capabilities are emerging concurrent with improvements that enable less use of fluoroscopy, Fox noted. In addition, more advanced mobile C-arms are empowering other clinicians to migrate into areas once dominated by specialists, such as cardiovascular surgeons, which arouses continual debate within the industry.

Limitations that Linger

While mobile C-arms have made significant strides they still have some hurdles to jump.
“Mobile C-arms today are still limited to X-ray based images,” Anderson said. “This type of image can sometimes contribute to lost anatomical information leading to wrong or misdiagnosis. With the introduction of multiple-based imaging systems (3-D imaging, color imaging, soft tissue, and intra-operative tissue imaging [muscular]) C-arms are evolving into single equipment, multiple-use units that can be changed easily from modality to modality by the user.”
Maneuvering in limited space remains a challenge, too, according to Trierweiler.
“In the O.R., space is at a premium, so size, weight and maneuverability are key. Two of the major limitations of C-arms are still size and weight because these affect maneuverability,” he said. “Since C-arms must be counterbalanced in all movements of the ‘C,’ new ideas would need to emerge in order to facilitate a lightweight design.”
Manum concurred. “As the amount of equipment in procedure rooms has increased, space has become more precious and the large size of most mobile C-arms has become an impediment to productivity,” he said. ‘Philips has addressed this issue by substantially reducing the C-arm’s mobile viewing station and introducing the concept of user-positionable LCD monitors. Next generation systems must be extremely portable and as inconspicuous as possible in the O.R., taking up a minimum of space and connecting seamlessly to monitors, networks and printers.
The emerging and growing bariatric patient population poses difficulties, sources indicated.
“A major point of emphasis for Philips has been the adaptation of our technology to keep pace with the special challenges posed by overweight and obese patients,” Manum said. “We have responded by boosting the size of the X-ray generator and modifying X-ray technique to get the best possible images on large patients.”
Indeed, obesity strains X-ray power, Trierweiler noted. “Weight constraints make it difficult to further increase the X-ray power,” he added.
Another limitation is that clinicians mainly use mobile C-arms today to image high-contrast objects, such as bones, according to Trierweiler. “The clinical benefits and potential of soft tissue contrast has to be further explored and clinically proven.”
More advances surgical procedures are driving the need for mobile C-arm advancements, according to Fox. “What we see happening in surgery is the emergence of more complex procedures, specifically minimally invasive procedures that spare muscle and tissue,” Fox said. “These procedures can create complications and workflow issues. Mobile C-arm technology has to take this into account. That’s why we’re bringing in more power and fixed-room capabilities into the mobile C-arms used in the O.R.”

Defining Moments to Come

Despite their former and existing limitations mobile C-arms face a C-worthy future in terms of reliability and usefulness as the technology progresses further. One impetus: DICOM.
“Like other imaging modalities, mobile C-arms have embraced the digital world and have allowed users to do away with the hassle and expense of film,” Manum said. “While Philips still sells printers and digital video recorders with its C-arms, many customers are going completely filmless by storing in DICOM format to a PACS network or workstation. In addition, it is now possible to query PACs and view pre-procedure images on the C-arm.”
Anderson agreed that DICOM integration is driving mobile C-arms’ clinical and financial legacy, and opening doors to outpatient opportunities. “With the current medical reimbursements as they are, doctors are finding it advantageous to perform procedures outside large hospitals,” he said. “Having DICOM-based C-arms allows the surgeon to take the information network to various operating rooms. Even though these procedures are being performed in the outpatient setting they still need to have access to the hospital base information system. This is accomplished by utilizing DICOM options that allow for full PACS integration.
“Hospitals are also finding that to compete with the outpatient facilities they must open their own clinics where PACS integration is still vital,” he added.
“One of the drawbacks of mobile C-arms is the use of image intensifiers as an imaging detector due to image distortion,” Trierweiler noted. “However, there are [image intensifiers] available with a complete Mu-metal shielding that virtually eliminate image distortion caused by the Earth’s magnetic field. [Image intensifiers], by nature, are vacuum devices with limited life expectancy. The foreseeable alternatives to [image intensifiers] are flat-panel detectors, which are by nature distortion-free.
“When flat-panel detectors become more affordable for the price-sensitive mobile C-arm market, this new technology will provide imaging without distortion and will allow for new designs yielding improved patient access,” he concluded.

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